An interferometric measuring device of this type is described in German Published Patent Application No. 41 08 944 (where the scanning of an intermediate image given as an alternative in the present document is not mentioned). With this interferometric measuring device based on the measuring principle of white-light interferometry or short-coherence interferometry, a radiation source emits short-coherent radiation which is split by a beam splitter into an object beam which illuminates a measuring object and a reference beam which illuminates a reflective reference plane in the form of a reference mirror. To scan the object surface in the depth direction, the reference mirror is moved in the direction of the optical axis of the reference light path by a piezo control element. When the object light path corresponds to the reference light path, the maximum interference contrast is obtained in the area of the coherence length and is detected by a photoelectric image converter and a downstream analyzing device and is analyzed on the basis of the known deflection position of the reference mirror to determine the contour of the object surface.
Additional interferometric measuring devices and interferometric measuring methods based on white-light interferometry are described by P. de Groot, L. Deck, “Surface profiling by analysis of white-light interferograms in the spatial frequency domain” J. Mod. Opt., Vol. 42, No. 2,389-401, 1995 and Th. Dresel, G. Häusler, H. Venzke, “Three-dimensional sensing of rough surfaces by coherence radar,” Appl. Opt., Vol 31 no. 7,919-925, 1992.
In German Patent Application No. 199 48 813 (not pre-published) such an interferometric measuring device based on white light interferometry is also shown, the lateral resolution being increased particularly for measurement in narrow cavities by creating an intermediate image in the objective light path. German Patent Application No. 100 15 878.1, likewise not published previously, proposes scanning of an intermediate image to increase the depth of focus, with a relatively high lateral resolution at the same time.
There are problems with the current interferometric measuring devices and measuring methods if the measurement task requires scanning of several separated surfaces which are several millimeters apart, for example, and/or are oriented at an inclination to one another.